26 citations · 55 across the 41 of their papers we have counts for
4 papers · 1 filter
Two remarks about nilpotent operators of order two
Stephan Ramon Garcia, Bob Lutz, Dan Timotin
We present two novel results about Hilbert space operators which are nilpotent of order two. First, we prove that such operators are indestructible complex symmetric operators, in…
The numerical range of a contraction with finite defect numbers
Hari Bercovici, Dan Timotin
An n-dilation of a contraction T acting on a Hilbert space H is a unitary dilation acting on H \oplus C^n. We show that if both defect numbers of T are equal to n, then the closure…
A note on composition operators in a half-plane
Hari Bercovici, Dan Timotin
Conditions for a composition operator on the Hardy space of the disk to have closed range or be similar to an isometry are well known. We provide such conditions for composition op…
Factorizations of analytic self-maps of the upper half-plane
Hari Bercovici, Dan Timotin
We extend a factorization due to Krein to arbitrary analytic functions from the upper half-plane to itself. The factorization represents every such function as a product of fractio…